Discovery of a novel small molecule inhibitor targeting the frataxin/ubiquitin interaction via structure-based virtual screening and bioassays

J Med Chem. 2013 Apr 11;56(7):2861-73. doi: 10.1021/jm3017199. Epub 2013 Mar 29.

Abstract

Friedreich's ataxia (FRDA) is an autosomal recessive neuro- and cardiodegenerative disorder for which there are no proven effective treatments. FRDA is caused by decreased expression and/or function of the mitochondrial protein frataxin. Here, we report findings that frataxin is degraded via the ubiquitin-proteasomal pathway and that it is ubiquitinated at residue K(147) in Calu-6 cells. A theoretical model of the frataxin-K(147)/Ub complex, constructed by combining bioinformatics interface predictions with information-driven docking, revealed a hitherto unnoticed, potential ubiquitin-binding domain in frataxin. Through structure-based virtual screening and cell-based assays, we discovered a novel small molecule (compound (+)-11) able to prevent frataxin ubiquitination and degradation. (+)-11 was synthesized and tested for specific binding to frataxin by an UF-LC/MS based ligand-binding assay. Follow-up scaffold-based searches resulted in the identification of a lead series with micromolar activity in disrupting the frataxin/Ub interaction. This study also suggests that frataxin could be a potential target for FRDA drug development.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Assay
  • Blotting, Western
  • Chromatography, Liquid
  • Drug Discovery*
  • Frataxin
  • HEK293 Cells
  • Humans
  • Iron-Binding Proteins / antagonists & inhibitors*
  • Iron-Binding Proteins / chemistry
  • Mass Spectrometry
  • Models, Molecular
  • Small Molecule Libraries*
  • Structure-Activity Relationship
  • Ubiquitin / antagonists & inhibitors*
  • Ubiquitin / chemistry

Substances

  • Iron-Binding Proteins
  • Small Molecule Libraries
  • Ubiquitin